This invention relates to swash-plate type compressors for compressing refrigerant gas in air conditioning systems, and more particularly to improvements in lubricating oil feeding means used in such compressors, which is capable of smoothly introducing lubricating oil contained in the refrigerant gas into the swash plate chamber.
In a swash-plate type compressor of this kind in general, rotation of the swash plate which is obliquely secured on the drive shaft causes reciprocating motions of the pistons within their respective cylinder bores to carry out pumping actions in cooperation with the suction valves and discharge valves. The swash plate and the pistons engage with each other, with balls and shoes slidably interposed therebetween, in a manner such that rotation of the swash plate is smoothly transduced into reciprocating motions of the pistons. According to this arrangement, the swash plate, the shoes, the balls and the pistons have their sliding contact portions subjected to severe friction and therefore require to be always fed with lubricating oil.
To effect lubrication of the sliding contact portions, a swash-plate type compressor has been proposed, e.g. by Japanese Provisional Patent Publication No. 57-65887, which is adapted to introduce part of the suction refrigerant gas into the swash plate chamber accommodating the swash plate, to supply the sliding contact portions with the lubricating oil contained in the refrigerant gas.
With compressors of the above kind, as the rotational speed of the compressor increases, the compressor delivery, i.e. the amount of refrigerant gas discharged from the compressor, increases to enhance the cooling or refrigerating capacity of the associated cooling or refrigerating cycle. Therefore, when the cooling or refrigerating capacity exceeds a desired level, it can result in large energy loss of the compressor and freeze-up of the evaporator. to avoid the disadvantage, a variable delivery type compressor has been proposed, e.g. by Japanese Provisional Patent Publication No. 52-96407, wherein a damper responsive to pressure changes is arranged in the vicinity of the suction port so that when the pressure in the vicinity of the suction port drops during high speed operation of the compressor, the damper is displaced in response to the pressure drop to reduce the cross-sectional area of the flow passage of the suction refrigerant gas, thereby decreasing the delivery of the compressor.
However, even in a compressor employing one or both of these proposed arrangements, in which the lubricating oil contained in the refrigerant gas is used to lubricate the sliding contact portions within the swash plate chamber, introduction of the refrigerant gas into the swash plate chamber is impeded by the swash plate swingingly rotating in the swash plate chamber at a high speed, resulting in an insufficient amount of the refrigerant gas flowing into the swash plate chamber. Further, the amount of the refrigerant gas flowing into the swash plate chamber decreases with an increase in the rotational speed of the compressor. Consequently, these conventional compressors are not free of the disadvantages that only a small amount of the lubricating oil is supplied to the sliding contact portions within the swash plate chamber and in addition, its amount decreases during high speed operation of the compressor wherein the supply of lubricating oil to the sliding contact portions is particularly required.